What truly defines love?

I am watching the same movie for the several time: A beautiful Mind, the story about John Nash without whom we wouldn't have any development in Game Theory, hence no interpretation of some very important economic behavior in personal and group bases.

I go through the dialogue for the immense time and try to understand the reasoning of this great mind. Here...

• Nash: I find you very attractive. Your aggressive moves toward me indicate that you feel the same way. But still, ritual requires that we go through a number of platonic activities before we
  [brief pause]... have sex. I'm simply proceeding with those activities. But in point of actual fact, all I really want to do is have intercourse with you as soon as possible. You're gonna slap me now.


• Nash: I don't exactly know what I am required to say in order for you to have intercourse with me. But could we assume that I said all that. I mean essentially we are talking about fluid exchange right? So could we go just straight to the sex.

Hiis sarcasm suggests me nothing but action. At this point of developments there is a simple reasoning which simply "saves lots of times" but gives "lots of trouble". The simple reasoning t is not appreciated at all and concluded with a slap in the face.



While he is searching along his days the "original piece of work"so much demanded and expected that would justify his label (he was recommended by his professor for the university with a simple sentence "He is a genius!", he comes with a shocking statement. The answer to the questions: What truly is logic? Who defines reason? he responds in a rather menish way.So, at another part of the dialogue the conclusion is drawn and the curtains are again up for me:

• Nash: I've made the most important discovery of my life. It's only in the mysterious equation of love that any logical reasons can be found. I'm only here tonight because of you. You are the only reason I am... you are all my reasons.

Questions I raised to myself: Is it truly love that defines the reason, or is it the only feeling that we find reasonable to believe in and thus give it the remarks, valor and merits? Yet, we are almost sure that it is love the one that breaks all equations and creates one of his own taking the recent out of the borders of logic and leaving it with a simple statement, completely naked at the eyes of the world: "Love is blind!" or further as Pascal stated: "Love has its own reasons which reason itself does not recognize."

Do we value love because it is the only sustainable "thing" at which we count on? Can we do without? In the picture I've found to illustrate my thoughts, Goya makes it difficult for the eyes of the admirer to believe reason is the path to salvation. It looks to me like it's screaming: "Reason is demon!"

I couldn't take Nash for granted so I went through Alica's thoughts. At the end she is a woman and often we hear people saying women cannot do without love. Can they?

• Nash: Alicia, does our relationship warrant long-term commitment? I need some kind of proof, some kind of verifiable, empirical data.
  
• Alicia: I'm sorry, just give me a moment to redefine my girlish notions of romance.

She is surely standing up to her girlish romance definitions as we see her right beside to Nash while he is prized, but was it reason or love that kept her there?

Now that is a question that needs an answer which I'm still looking for. Are the girlish voices of romance the voices of reason that we should listen at or are they the old demons of old times when the world used to shine and rise only?

What truly defines reason?